RE: Patching

["Graydon McKee" <graydon.s.mckee.iv () orcmacro com>]

I'm getting into this discussion a bit late here but I thought I'd put
my two cents in.  

There seems to be at least 5 or 6 new vulnerabilities released on
BUGTRAQ or similar mailing lists daily.  As information security people,
or just regular systems administrators for that matter, we need to keep
on top of each of these to see if they apply to the systems we control.
Look at all the worms and viruses that have come out that exploit
vulnerabilities that have been known about for months or sometimes even
years.  Without patching our systems we are not only open to the newer
crop of vulnerabilities but all the old ones as well.  

If you have a concern about a system being vulnerable then you can take
a couple of steps.  Turn off every service you don't need running on a
given system.  Decide what is mission critical and turn off everything
else.  If you are not sure what services you need, turn them off and see
what breaks.  I know that is sometimes easier said than done. If your
UNIX based machine has the sendmail daemon enabled and its not acting as
a mail server - turn it off.  If Mail is sent out from that machine the
mail client runs the sendmail executable directly from the disk it
doesn't need the daemon running.  Set a cron job to periodically process
the queue or drop the -bd switch from the boot script but its something
that can be turned off.  

Once you have everything turned off that you don't need then take a look
at those patches you need for what you do have running.  Install those
patches and make note of the patches for the services you turned off
incase you ever need to turn them back on again.  

The point is that you still need to pay attention to patches.  If your
system is exploited and damage is actually done, the excuse that you
didn't patch it because you thought it could have caused a problem
doesn't hold water.  Do a full backup and then patch the system.  If it
breaks then restore your backup and your back to square one.  

Just my two cents. 

Graydon S McKee IV
Firewall/Security Administrator
ORC Macro - Macro International
11785 Beltsville Drive
Calverton, Maryland 20705
301-572-0583 Fax: 301-572-0982


-----Original Message-----
From: Ansgar -59cobalt- Wiechers [mailto:bugtraq () planetcobalt net] 
Sent: Wednesday, October 22, 2003 6:58 AM
To: security-basics () securityfocus com
Subject: Re: Patching

On 2003-10-21 Alessandro Bottonelli wrote:
> On Tuesday 21 October 2003 10:33, Ansgar -59cobalt- Wiechers wrote:
> > On 2003-10-20 Alessandro Bottonelli wrote:
> > > Hmmmm. I am not convinced yet that all this makes sense from a
> > > "wider" security perspective. Must a vulnerability / hole be known
> > > to be a risk?
> >
> > Yes.
>
> The more I think about it, the more I do not agree. Security is
> availability, confidentiality and integrity, isn't it? An unknown hole
> / vulnerability can still hit you hard (data loss, data integrity,
> system availability to name a few instances). Humans may not know
> about such vulnerability but systems run that code, and if the code is
> flawed, systems do not need humans to fail or to behave incorrectly
> from a security perspective. 

Availability, confidentiality and integrity are separate issues that
have to be addressed in different ways. When talking about security (at
least on this list) the majority is referring to confidentiality and
partly integrity (to the extent that data isn't manipulated by
unauthorized persons). At least that's my perception. Please correct me
if I'm wrong.

You are right that might affect availability and/or integrity and that
those issues need to be taken into consideration, but AFAIK they are
usually not considered _security_ risks.

[...]
> Was the price of closing a known hole that maybe someone one day might
> have exploited (and maybe I might have had another option for
> proctecting my systems) worth a failed Disaster Recovery?

Deal with that problem when you run into it. That's what you test
patches for. There is no point in avoiding a patch just because it
*might* break something.

If it breaks something you will have to make a decision whether to apply
it (and forfeit on some functionality) or not (and face the risk of
getting 0wnzed). That decision can only be made for each individual
incident.

If anyone happens to have a golden rule here, I'd like to know too ;)

> I am not saying patching is evil, but is dawning on me the idea that
> is not "necessarily" good, or in other words its worthness is not
> axiomatic.

It may rise other problems, but it gets you rid of a security breach
that is known to the world. That's the only point I was referring to.

> The list suggested a testbed system should be used for testing patches
> before going onto production systems. This would be a good step
> forward in making patches less dangerous, yet many organizations (or
> at least most of those I deal with) cannot (or do not want to) afford
> such luxury which requires a duplicate system, time and human
> resources (and even then I wonder how thorough and reliable a test
> would be on a non-production system, probably not fully interconnected
> with the whole infrastructure).

There has been a discussion on this a while ago, and there were some
valuable suggestions (e.g. using VMware). You might want to take a look
into the list's archive.

Regards
Ansgar Wiechers

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